.MUM File Extension

Windows Vista Update Package

MUM files are used by the Microsoft Windows System Update in order to update programs, drivers, and Windows system files. These are essentially archive files which contain the entire set of files needed to do a hotfix or update to various areas of the system. The files included in MUMs include the installer for the update or hotfix, DLLs that may be needed, INF files that may be needed, and any accessory EXEs that may have shipped with the update.